738 FUCHT international, II May
HANDLEY PAGE JETSTREAM . . .
Specification
By 1970, Handley Page estimate, the turbine-engined American
business aviation fleet will have risen from today's figure of
about 1,000 aircraft to over 3,700. Whereas less than a quarter
of the current turbine fleet is in the under $500,000-a-piece
bracket (the majority being $500,000-$ 1 million twin jets) this
category is expected to assume more like 60 per cent of the
total by the turn of the decade. The big development of the
next three years is going to be the appearance of six-seat
turboprops in the under $300,000 bracket (where only the
Mitsubishi MU-2B exists at present)—turboprop versions of
the Piper Navajo, Beechcraft Duke, Cessna 401 and Ted Smith
Aerostar series being the most advanced in preparation. But the
best immediate sales prospects are in the intermediate price
bracket ($3OO,OOO-$5OO,OOO) where the present fleet of 200
or so Beechcraft King Airs, Aero Commander Turbo Com-
manders and Swearingen Merlins should swell to nearly 1,000
aircraft. It is here that the Jetstream promises to do extremely
well.
At a price not much more than that of the King Air the Jet-
stream's principal offering compared with those of its three
closest rivals is its combination of more capacity, better range-
payload, higher speed and greater comfort. The latter may be
likened to that between the HS.125 and Falcon "walkabout jets"
and the "get in and sit down" Lear Model 24 and Jet Com-
mander. In fact, judging from the mock-up, the Jetstream has
all the space, style and impressiveness of the big Grumman
Gulf stream. In determining the basic design parameters it was
decided to go for the largest practicable passenger capacity in
order that the aircraft should command the widest posssible
application in the business and air taxi/feederliner markets and
also have a military potential.
Price and airfield performance requirements dictated that the
HP. 137 should be a turboprop rather than a jet; piston engines
were rejected for their inferior thrust/weight ratio. The highly
developed and very efficient Turbomeca Astazou XIV fixed-
shaft engine was chosen because it was the only engine of the
right size. The airframe characteristics were then broadly
determined by the desired airfield performance (operation from
runways of less than 3,500ft) and a range/cruising speed of
1,500 miles (one-stop US coast-coast) at 300 m.p.h. The fuse-
lage was schemed in order that it could seat three abreast and
so that a high proportion of the disposable load (actually
77 per cent) could be carried as passengers—a feature that is
most attractive to commercial operators. With a gross weight
limited to 12,5001b (to stay within the simplified commercial
operating rules for light aircraft) this meant providing space
for 18 passengers. There is fuselage stretch potential for at
least a 24-seat capacity if need be. Finally, all of this was to
be achieved at a price of about £150,000 ($420,000) ex-works
for the basic aircraft to stay competitive with the other turbo-
props and to be significantly cheaper than the smaller twin jets.
That Handley Page may well have scored a major break-
through with an incredibly conventional aeroplane is about
to be put to the test with the first flight. Market reaction is
one of confidence—165 aircraft booked, Government financial
support to the tune of over £1 million and a loan-stock of over
£1 million subscribed 2£ times by existing shareholders.
Powerplant
Design The 850 e.s.h.p. Turbomeca Astazou XIV chosen
for the Jetstream is the newest and most powerful development
in this eight-year-old series of engines that have become noted
for their efficiency. Important changes made for this installa-
tion are aimed at reducing the operating noise level on the
ground (previous Astazous ran at 100 per cent r.p.m. the
whole time), and to generally enhancing powerplant control
system reliability and performance. The former is being
attempted by introducing some control over engine r.p.m. and
by having the lowest possible output shaft r.p.m. from the
reduction gearbox (1,783 r.p.m. as opposed to the 2,066 r.p.m.
of the Astazou XII). To improve engine control the electrical
system has been entirely replaced by hydraulics comprising,
essentially, a Hamilton Standard hydraulic constant speed pro-
peller-hub unit, and a pressure-sensed, hydraulkally trans-
mitted, thermal load limiter.
The basic Astazou XIV engine first ran last autumn, is now
well on with certification trials at the CEP Saclay, and type
approval is imminent A fully representative Jetstream power-
plant including the three-bladed Hamilton Standard propeller
and the new control system, will begin flight trials in an Eper-
vier test aircraft this month. When the engine enters service it
is expected that it will be cleared for a l.OOOhr life between
overhauls.
As well as being of the right size and price for the Jetstream
the Astazou XIV offered the best specific weight and specific
fuel consumption of aH the engines available; it also appealed
for its compactness (maximum diameter being only just over
20in). The popular Garrett TPE-331 and P&W PT6A engines
were judged too small for the job while the BS Gnome had the
advantage of power but the higher weight would have pre-
cluded a gross weight for the aircraft of less than 12,5001b.
The constant-speed fixed-shaft design of the Astazou is the
key to its extremely good specific performance; by being able
to keep the compressor surge margin small the result was an
unusually compact, robust and efficient compressor unit com-
prising two axial stages (with low aspect ratio blades running
at transonic speeds) followed by a centrifugal stage, to give a
compression ratio of 8:1 (compared to 6:1 of most small tur-
bines). The annular combustion chamber is followed by a
three-stage turbine. Engine r.p.m. is maintained constant at
43,000 r.p.m. (except on the ground when this is reduced to
85 per cent for taxying, and to 65 per cent for idling) and is
delivered through two-stage reduction gears to give 1,783 r.p.m.
at the propeller shaft. Fuel flows along the main shaft from
the front and enters the combustion chamber via a slinger disc
for adequate vaporisation without the need for unduly small
injection nozzles.
A three-bladed Hamilton Standard propeller with hydraulic
operation of the pitch-change mechanism has been chosen. The
23LF hub uses engine oil pressure to move the blades towards
T«xt continued on page 742, after cutaway drawing of J«t»tr«am
There are eight standard interior layouts of the Jetstream cabin-
seven spacious luxury arrangements for private use (typical eight
seater, upper plan) and an 18-seat high-density version for com-
mercial operators (lower plan)
mmm mrnm
JETSTREAM DATA
Powerplant Two 850 e.s.h.p. Turbomeca Astazou XIV fixed-shaft turboprop
engines driving Hamilton Standard three-bladed variable-pitch fully feathering
propellers hydrautieally actuated.
Dimension* Span, 52ft; length, 47ft l.5in; height 17ft 5in; wing area, 270 sq fc
aspect ratio, 10 : I; dihedral, 7"; undercarriage track, 19ft oin; wheelbase, 15" ">•
Weight! Gross, 12,5001b; maximum landing, I2,500lb; aircraft prepared for
service (executive layout), 8,9701b; aircraft prepared for service (high-densa
layout), 8,2001b; maximum payload (freight), 4,0001b; fuel capacity, 390 Imp I
total.
Accommodation Cabin length (excl flight deck), 24ft 3in; cabin width (mtx
internal), 6ft tin; aisle headroom, 5ft 11 in; executive layout seating capaci
8, 9, 10 and 12; high-density seating capacity, 18.
Performance See charts on page 739.